package main

import (
	"context"
	"fmt"
	"time"

	"golang.org/x/time/rate"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	kubeinformers "k8s.io/client-go/informers"
	appsinformers "k8s.io/client-go/informers/apps/v1"
	"k8s.io/client-go/kubernetes"
	k8sClientSet "k8s.io/client-go/kubernetes"
	"k8s.io/client-go/kubernetes/scheme"
	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/workqueue"
	"k8s.io/klog/v2"

	demov1 "github.com/ygong3/dev-k8s-controller/pkg/apis/demo1.test.io/v1"
	clientset "github.com/ygong3/dev-k8s-controller/pkg/generated/clientset/versioned"
	demo1ClientSet "github.com/ygong3/dev-k8s-controller/pkg/generated/clientset/versioned"
	demoscheme "github.com/ygong3/dev-k8s-controller/pkg/generated/clientset/versioned/scheme"
	demo1Informers "github.com/ygong3/dev-k8s-controller/pkg/generated/informers/externalversions"
	informers "github.com/ygong3/dev-k8s-controller/pkg/generated/informers/externalversions/demo1.test.io/v1"
	listers "github.com/ygong3/dev-k8s-controller/pkg/generated/listers/demo1.test.io/v1"
)

// ProductController is the controller implementation for Product resources
type ProductController struct {
	// kubeclientset is a standard kubernetes clientset
	kubeclientset kubernetes.Interface
	// demo1clientset is a clientset for our own API group
	demo1clientset clientset.Interface
	productsLister listers.ProductLister
	productsSynced cache.InformerSynced

	// workqueue is a rate limited work queue. This is used to queue work to be
	// processed instead of performing it as soon as a change happens. This
	// means we can ensure we only process a fixed amount of resources at a
	// time, and makes it easy to ensure we are never processing the same item
	// simultaneously in two different workers.
	workqueue workqueue.TypedRateLimitingInterface[cache.ObjectName]
	// recorder is an event recorder for recording Event resources to the
	// Kubernetes API.
	recorder record.EventRecorder
}

func runProductController(kubeClientSet *k8sClientSet.Clientset, config *rest.Config, stopCh chan struct{}) {
	demo1Client, err := demo1ClientSet.NewForConfig(config)
	if err != nil {
		logger.Error(err, "Error building kubernetes clientset")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}

	kubeInformerFactory := kubeinformers.NewSharedInformerFactory(kubeClientSet, time.Second*30)
	exampleInformerFactory := demo1Informers.NewSharedInformerFactory(demo1Client, time.Second*30)

	controller := NewProductController(ctx, kubeClientSet, demo1Client,
		kubeInformerFactory.Apps().V1().Deployments(),
		exampleInformerFactory.Demo1().V1().Products())

	// notice that there is no need to run Start methods in a separate goroutine. (i.e. go kubeInformerFactory.Start(ctx.done())
	// Start method is non-blocking and runs all registered informers in a dedicated goroutine.
	kubeInformerFactory.Start(ctx.Done())
	exampleInformerFactory.Start(ctx.Done())

	if err = controller.Run(ctx, 2); err != nil {
		logger.Error(err, "Error running controller")
		klog.FlushAndExit(klog.ExitFlushTimeout, 1)
	}
}

// NewProductController returns a new sample controller
func NewProductController(
	ctx context.Context,
	kubeclientset kubernetes.Interface,
	demo1clientset clientset.Interface,
	deploymentInformer appsinformers.DeploymentInformer,
	productInformer informers.ProductInformer) *ProductController {
	logger := klog.FromContext(ctx)

	// Create event broadcaster
	// Add sample-controller types to the default Kubernetes Scheme so Events can be
	// logged for sample-controller types.
	utilruntime.Must(demoscheme.AddToScheme(scheme.Scheme))
	logger.V(4).Info("Creating event broadcaster")

	eventBroadcaster := record.NewBroadcaster(record.WithContext(ctx))
	eventBroadcaster.StartStructuredLogging(0)
	eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: kubeclientset.CoreV1().Events("")})
	recorder := eventBroadcaster.NewRecorder(scheme.Scheme, corev1.EventSource{Component: controllerAgentName})
	ratelimiter := workqueue.NewTypedMaxOfRateLimiter(
		workqueue.NewTypedItemExponentialFailureRateLimiter[cache.ObjectName](5*time.Millisecond, 1000*time.Second),
		&workqueue.TypedBucketRateLimiter[cache.ObjectName]{Limiter: rate.NewLimiter(rate.Limit(50), 300)},
	)

	controller := &ProductController{
		kubeclientset:  kubeclientset,
		demo1clientset: demo1clientset,
		productsLister: productInformer.Lister(),
		productsSynced: productInformer.Informer().HasSynced,
		workqueue:      workqueue.NewTypedRateLimitingQueue(ratelimiter),
		recorder:       recorder,
	}

	logger.Info("Setting up event handlers")
	// Set up an event handler for when Product resources change
	productInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: controller.enqueueProduct,
		UpdateFunc: func(old, new interface{}) {
			controller.enqueueProduct(new)
		},
	})
	return controller
}

// Run will set up the event handlers for types we are interested in, as well
// as syncing informer caches and starting workers. It will block until stopCh
// is closed, at which point it will shutdown the workqueue and wait for
// workers to finish processing their current work items.
func (c *ProductController) Run(ctx context.Context, workers int) error {
	defer utilruntime.HandleCrash()
	defer c.workqueue.ShutDown()
	logger := klog.FromContext(ctx)

	// Start the informer factories to begin populating the informer caches
	logger.Info("Starting Product controller")

	// Wait for the caches to be synced before starting workers
	logger.Info("Waiting for informer caches to sync")

	if ok := cache.WaitForCacheSync(ctx.Done(), c.productsSynced); !ok {
		return fmt.Errorf("failed to wait for caches to sync")
	}

	logger.Info("Starting workers", "count", workers)
	// Launch two workers to process Product resources
	for i := 0; i < workers; i++ {
		go wait.UntilWithContext(ctx, c.runWorker, time.Second)
	}

	logger.Info("Started workers")
	<-ctx.Done()
	logger.Info("Shutting down workers")

	return nil
}

// runWorker is a long-running function that will continually call the
// processNextWorkItem function in order to read and process a message on the
// workqueue.
func (c *ProductController) runWorker(ctx context.Context) {
	for c.processNextWorkItem(ctx) {
	}
}

// processNextWorkItem will read a single work item off the workqueue and
// attempt to process it, by calling the syncHandler.
func (c *ProductController) processNextWorkItem(ctx context.Context) bool {
	objRef, shutdown := c.workqueue.Get()
	logger := klog.FromContext(ctx)

	if shutdown {
		return false
	}

	// We call Done at the end of this func so the workqueue knows we have
	// finished processing this item. We also must remember to call Forget
	// if we do not want this work item being re-queued. For example, we do
	// not call Forget if a transient error occurs, instead the item is
	// put back on the workqueue and attempted again after a back-off
	// period.
	defer c.workqueue.Done(objRef)

	// Run the syncHandler, passing it the structured reference to the object to be synced.
	err := c.syncHandler(ctx, objRef)
	if err == nil {
		// If no error occurs then we Forget this item so it does not
		// get queued again until another change happens.
		c.workqueue.Forget(objRef)
		logger.Info("Successfully synced", "objectName", objRef)
		return true
	}
	// there was a failure so be sure to report it.  This method allows for
	// pluggable error handling which can be used for things like
	// cluster-monitoring.
	utilruntime.HandleErrorWithContext(ctx, err, "Error syncing; requeuing for later retry", "objectReference", objRef)
	// since we failed, we should requeue the item to work on later.  This
	// method will add a backoff to avoid hotlooping on particular items
	// (they're probably still not going to work right away) and overall
	// controller protection (everything I've done is broken, this controller
	// needs to calm down or it can starve other useful work) cases.
	c.workqueue.AddRateLimited(objRef)
	return true
}

// syncHandler compares the actual state with the desired, and attempts to
// converge the two. It then updates the Status block of the Product resource
// with the current status of the resource.
func (c *ProductController) syncHandler(ctx context.Context, objectRef cache.ObjectName) error {
	logger := klog.LoggerWithValues(klog.FromContext(ctx), "objectRef", objectRef)
	logger.V(1).Info("Syncing Product resource", "objectReference", objectRef)

	// Get the Product resource with this namespace/name
	product, err := c.productsLister.Products(objectRef.Namespace).Get(objectRef.Name)
	if err != nil {
		// The Product resource may no longer exist, in which case we stop
		// processing.
		if errors.IsNotFound(err) {
			utilruntime.HandleErrorWithContext(ctx, err, "Product referenced by item in work queue no longer exists", "objectReference", objectRef)
			return nil
		}

		return err
	}

	stock := product.Spec.Stock
	if stock <= 0 {
		// We choose to absorb the error here as the worker would requeue the
		// resource otherwise. Instead, the next time the resource is updated
		// the resource will be queued again.
		utilruntime.HandleErrorWithContext(ctx, nil, "Stock is out of shortage, need add more products", "objectReference", objectRef)
		return nil
	}

	product.Spec.Stock = stock - 1
	// update product stock
	_, err = c.demo1clientset.Demo1V1().Products(product.Namespace).Update(ctx, product, metav1.UpdateOptions{FieldManager: FieldManager})
	if err != nil {
		utilruntime.HandleErrorWithContext(ctx, err, "Failed to update Product resource", "objectReference", objectRef)
		return err
	}

	// If an error occurs during Get/Create, we'll requeue the item so we can
	// attempt processing again later. This could have been caused by a
	// temporary network failure, or any other transient reason.
	if err != nil {
		return err
	}

	// If an error occurs during Update, we'll requeue the item so we can
	// attempt processing again later. This could have been caused by a
	// temporary network failure, or any other transient reason.
	if err != nil {
		return err
	}

	// Finally, we update the status block of the Product resource to reflect the
	// current state of the world

	c.recorder.Event(product, corev1.EventTypeNormal, SuccessSynced, MessageResourceSynced)
	return nil
}

// enqueueProduct takes a Product resource and converts it into a namespace/name
// string which is then put onto the work queue. This method should *not* be
// passed resources of any type other than Product.
func (c *ProductController) enqueueProduct(obj interface{}) {
	if objectRef, err := cache.ObjectToName(obj); err != nil {
		utilruntime.HandleError(err)
		return
	} else {
		c.workqueue.Add(objectRef)
	}
}

// handleObject will take any resource implementing metav1.Object and attempt
// to find the Product resource that 'owns' it. It does this by looking at the
// objects metadata.ownerReferences field for an appropriate OwnerReference.
// It then enqueues that Product resource to be processed. If the object does not
// have an appropriate OwnerReference, it will simply be skipped.
func (c *ProductController) handleObject(obj interface{}) {
	var object metav1.Object
	var ok bool
	logger := klog.FromContext(context.Background())
	if object, ok = obj.(metav1.Object); !ok {
		tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			// If the object value is not too big and does not contain sensitive information then
			// it may be useful to include it.
			utilruntime.HandleErrorWithContext(context.Background(), nil, "Error decoding object, invalid type", "type", fmt.Sprintf("%T", obj))
			return
		}
		object, ok = tombstone.Obj.(metav1.Object)
		if !ok {
			// If the object value is not too big and does not contain sensitive information then
			// it may be useful to include it.
			utilruntime.HandleErrorWithContext(context.Background(), nil, "Error decoding object tombstone, invalid type", "type", fmt.Sprintf("%T", tombstone.Obj))
			return
		}
		logger.V(4).Info("Recovered deleted object", "resourceName", object.GetName())
	}
	logger.V(4).Info("Processing object", "object", klog.KObj(object))
	if ownerRef := metav1.GetControllerOf(object); ownerRef != nil {
		// If this object is not owned by a Product, we should not do anything more
		// with it.
		if ownerRef.Kind != "Product" {
			return
		}

		order, err := c.productsLister.Products(object.GetNamespace()).Get(ownerRef.Name)
		if err != nil {
			logger.V(4).Info("Ignore orphaned object", "object", klog.KObj(object), "order", ownerRef.Name)
			return
		}

		c.enqueueProduct(order)
		return
	}
}

// newConfigMap creates a new Deployment for a Product resource. It also sets
// the appropriate OwnerReferences on the resource so handleObject can discover
// the Product resource that 'owns' it.
func newConfigMap(product *demov1.Product) *corev1.ConfigMap {
	labels := map[string]string{
		"app":        "nginx",
		"controller": product.Name,
	}
	return &corev1.ConfigMap{
		ObjectMeta: metav1.ObjectMeta{
			Name:      product.Spec.Name,
			Namespace: product.Namespace,
			OwnerReferences: []metav1.OwnerReference{
				*metav1.NewControllerRef(product, demov1.SchemeGroupVersion.WithKind("Product")),
			},
			Labels: labels,
		},
		Data: map[string]string{
			"description": product.Spec.Description,
			"price":       fmt.Sprintf("%f", product.Spec.Price),
			"stock":       fmt.Sprintf("%d", product.Spec.Stock),
			"createdAt":   product.CreationTimestamp.String(),
			"updatedAt":   time.Now().Format(time.RFC3339),
		},
	}
}
